Acceptance inspection of new offset printing machi

2022-08-13
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Acceptance and inspection of new offset printing machines in the printing plant

with the gradual increase of the competitiveness of the printing market, the share of hard power in the printing unit is becoming more and more obvious, especially a printing machine with high cost performance brings great business opportunities to the printing unit, which can cope with the growing market demand, but whether the performance of the introduced new printing machine fully meets the needs of the company, how to accept the newly purchased printing machine, It is a key issue. The author has the honor to participate in the acceptance of the new printing machine in the printing company. Now I will share the acceptance results with my colleagues, hoping to give some enlightenment to the industry

I. acceptance work content

for manufacturers of large brand offset printing machines, they have been tested comprehensively before delivery. However, considering the price of the offset press and the requirements of our factory for production, some tests before acceptance are necessary, such as checking whether the offset press is in a stable working state after installation and commissioning; Check whether the performance and parameters of the offset press comply with the specifications. The author communicated with the experienced printer and the master who has worked in the printing production line for many years. It is believed that the acceptance of new printing machines mainly includes the following aspects

1. Empty operation

after connecting the power supply to the offset press, in order to check whether the installation and connection of each part of the equipment are normal, the operation speed of the equipment cannot be turned on very fast, but can only operate at a low speed. Then slowly increase the speed until it runs at the highest speed. First, listen to whether the offset press has abnormal sound; Second, check the vibration degree of the offset press. Put half a bottle of mineral water on each unit and observe whether the fluctuation of the water surface caused by vibration is abnormal

2.50% lithography test

generally speaking, the perimeter of 50% point is the largest, and the larger the perimeter is, the larger the point increases, so the point increase value is also the largest. Because of this, the 50% point increase value is one of the important indicators to evaluate the performance of offset press. The requirements for 50% flat are: the flat format is the maximum printing size; Flat itself is flat without stripes; The flat front mouth or trailing tip should preferably be able to bring a solid block, which can be used as the basis for the ink volume during the flat test

3. The field test version

the field test version is mainly to detect whether the printing pressure and rolling pressure meet certain standards. You can check whether each unit has a bar (including impact bar, ink bar, water bar, etc.). Since the 50% level is not obvious to the bar, the test of this link is still very necessary

4. Meter lattice overprint

meter lattice overprint is mainly to check the registration accuracy of the offset press and the reflection of the fan-shaped expansion of the paper. The following tests can be carried out: on the premise that the full page fine line overprint is basically accurate (the overprint accuracy can reach 0.01mm), then carry out a single test: first, print at different speeds, and check whether the overprint accuracy changes; Then print about 100 sheets of 80g/m2 paper, and observe the loose tail of thin paper printing, because the loose tail is related to the performance of the paper itself, which can only be used as a reference

5. Printing standard test edition

although the test edition used by various machines has various combinations and collocations, and there is no unified regulation, it will certainly contain two parts, namely, the objective measurement signal bar and the subjective evaluation picture, in order to complete the comprehensive evaluation of the printed matter. After discussion, considering the actual production situation of our factory, we decided to take the GATF color reproduction test chart as the sample, and then add some special images to carry out the acceptance of the offset press

II. Objective test content of beta version

tf/system digital layout control

this object is designed to be used along the outer edge of the test format. It is a multi-component detection and process control tool, including a, B, C, D, e, F and other parts, which is used to monitor digital output exposure system, film, printing plate, proofing, etc

a part includes image device confirmation, interpreter level, horizontal and vertical resolution, image direction, screen line number, point type, line angle

b is the resolution of the test system

The

c part is the minimum mark and minimum spacing of a given resolution

The

d part is used to detect the exposure conditions of the system. If the arc details of the positive and negative images are clear, it indicates that the system is good

The

e part is the star Mark and the ink field color block. The star mark is composed of wedge-shaped patterns with an interval of 5 degrees, which is mainly used to check the printing faults such as proofing, the expansion of printing time points, vertical and horizontal deformation, ghosting and plate pasting. The two color patches are 1501pi and 2001pi 50% points, which are used to evaluate the increase of color value of the system, and can also be objectively evaluated by reflection densitometer

The

f part is composed of two sets of matching step adjustment ladders. The upper one is the compensation program setting without rip application, and the lower one is the compensation setting application. The two ladders clearly show the impact of the compensation procedure. If the Pu insulation materials whose flame retardancy reaches B1 and B2 are consistent after the completion of two ladders, it indicates that there is no compensation program for rip

2. Gray balance scanning object

the gray balance scanning object contains a series of gray balance color blocks, which have the same value as the color blocks in the four areas of the gray balance table. These numbered color blocks are designed to be arranged along a straight line to facilitate the scanning of the densitometer. The color blocks with 90 degree and 180 degree peel number 1 are white paper for the calibration of the densitometer; The color blocks numbered 2 to 27 correspond to the signal area of the highlight; The color blocks numbered 28 to 64 correspond to the 1/4 tone signal area; The color blocks numbered 65 to 101 correspond to the signal area of the intermediate tone; The color blocks numbered 102 to 138 correspond to the 3/4 tone signal area. In the high light signal region sequence from 2 to 27, the green dot of each color block is 7%, while the range of magenta and yellow dot increases from 1% to 6%; In the 1/4 tone area, the green dot is 30%, while the range of pinprick and yellow dot is 16% to 28%; In the middle tone area, the green dot is 60%, and the range of product and yellow dot increases from 46% to 58%; In the 3/4 tone area, the green dot is 80%, and the pinprick and yellow dot increase from 66% to 78%

3. Scanning step ladder

for the six colors in the format of digital test page 4.1, each scanning step ladder contains a total of 22 halftone ink blocks and a field ink block. These color patches can be used to measure the point enlargement from 5% to 95% at equal intervals of 5%, and add 3% and 7% points in the light part and 97% points in the dark part as additional input to the gradient range of the critical part. These step-by-step ladders are better designed for process standardization than for process control and detection. In order to obtain effective data from the ladder ruler, the printing system must operate within the operating specifications. If a densimeter with microprocessor assistance is used to measure the point enlargement value, it will automatically measure the surface area. After 23 groups of data points are obtained from the scanning step ladder, it is easy to build a point enlargement value curve to describe the characteristics of the whole printing system. When halftone color separation printing is used in this system, the tolerance of point enlargement value determined by this curve should also be used. The advantage of using a scanning step ladder to create a point enlarged value curve is that its 23 data points make the curve highly accurate. It is associated with the digital page test format, which may optimize the printing conditions

8.7/3 basic data setting

include IT8.7/3 standard test draft in the digital page test format. Basic data settings are used for a large number of tests of third color reproduction, or the composition of three spot colors plus black. Choosing the color in it8 color setting can cover the whole color tone, and facilitate the conversion of color space and the drawing of full tone curve. The color block in the basic data list is jointly confirmed by the letters representing the column and the numbers representing the row (for example, B13 represents the color block in the 13th row of column B)

5. Six color double row control strip

the six color double row control strip is located at the edge of the starting part of the test format page, with two small blocks wide and 114 small blocks long. Its size is 0.39 22.47 inches (10.0 57.1 mm), the measured size of a single block is 0.20 0.20 inches (5.0 5.0mm), and the inking area is 1.18 inches (30mm) long. The upper layer arrangement is composed of field ink blocks, including 19 duplicate copies of CMYK, while the lower layer arrangement includes a white color block of the initial paper, followed by three color block repetitions of 25%, 50% and 75% of CMYK, followed by two star copies of CMYK, two copies of CMYK dot magnification Scale II, then blue, green and red overprint, and two copies of cmky ghosting/highlight targets, And the adjacent blue, green and red three color overprint field and 50% color

tf/RHEM light indicator

gatf/RHEM light indicator can be placed at the bottom of the test format page. It is used to confirm whether the ambient light is the recommended standard 5000K color temperature (according to ANSI pH 2.). GATF/RHEM light indicator is a pressure-sensitive adhesive, which has a stripe pattern painted with two formula inks. It is carefully configured to achieve optimal matching at 5000K color temperature, but it cannot match under the light of other color temperatures. As a warning pattern, this light indicator will give a warning when the evaluation program cannot make correct color judgment. Because subjective quality control depends on the color matching between different colorants (such as between thermal sublimation dyes and printing inks), and all judgments must be made under standard observation conditions (ANSI standard)

III. subjective evaluation pictures of beta version

1 Low key/red couch

the red couch is a low-key reference drawing. Its main tone is dark, including red, green, blue and a variety of perfect wood texture tones, which is located in the middle to low-key area of the tone reproduction curve. If you want to copy the dark tone image with this degree of detail, you need a high-resolution scanner and a large text, but the weld made of 4-block additive is well maintained, which has high requirements for color separation and prepress equipment. There is enough gradient compression to shift the middle tone part to the dark tone tail, and use lithography or direct digital printing to print, so as to have enough contrast to distinguish the dark tone color

2. High profile/wedding banquet

the photo of the wedding banquet is a light tone reference map, and its main tone is soft light and white, which is located in the high-profile to middle tone part of the tone reproduction curve. For such pictures, it is necessary to set the minimum printable gradient points (especially 3% points), have enough gradient compression, shift the middle tone to the highlight part, and use lithography or direct digital printing to achieve accurate reproduction, so as to have enough contrast to distinguish the bright tones

3. Group portrait/painting teenager

group portrait/painting teenager is the reference map of human skin color, in which white people, Latin Americans, Japanese, African Americans and Indians are in turn from left to right. The key to how to reproduce the five skin colors equally and perfectly is to choose the correct color correction to maintain these tones without causing the shift of gray balance

4. Portrait of women

the portrait of women is a reference picture of white women, which is a common example of portrait tone reproduction. The portrait of women is the focus of photo color printing. In order to maintain the details of dark parts of hair and clothes, and maintain the details of bright parts at the same time, in the process of color separation, UNIDO held an international conference in Shantou, its gray balance should be tilted to the direction of human tone reproduction to get correct compensation, so there will be subtle color changes in the parts from high light to middle tone

5. Neutral grey

medium

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